Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 21521 — Barton, MD

ZIP code 21521 (Barton, Allegany County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 29 and the first fall frost October 20.

Where ZIP 21521 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone6b−5 to 0 °F

Coldest night−20.6 to −17.8 °C

Last frostApr 29

First frostOct 20

2012 zone6b

Same zone as on the 2012 map. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Barton, MD…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Barton, MD

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostApril 29median — 50% chance of a later frost

Safe for tender plantsMay 15only 10% chance of frost after

First fall frostOctober 20median — 10% chance by Oct 4

Growing season174 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 12 and returns around November 1.

From the NOAA station Savage Rvr Dam, MD — 6 miles away, elevation 1,496 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 21521

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 18 – Apr 1

SpinachSow outdoors · Mar 18 – Apr 8

Broccoli, cabbageStart indoors · Feb 18 – Mar 4

Broccoli, cabbageTransplant · Apr 8 – Apr 22

Onion setsPlant outdoors · Apr 1 – Apr 15

PotatoesPlant outdoors · Apr 8 – Apr 22

LettuceSow outdoors · Apr 1 – Apr 15

Carrots, beetsSow outdoors · Apr 8 – Apr 22

TomatoesStart indoors · Mar 4 – Mar 18

TomatoesTransplant · May 6 – May 20

Peppers, eggplantStart indoors · Feb 18 – Mar 4

Peppers, eggplantTransplant · May 13 – May 27

BeansSow outdoors · May 6 – May 20

Sweet cornSow outdoors · May 6 – May 20

Cucumbers, squashSow outdoors · May 6 – May 20

Fall lettuce, spinachSow outdoors · Aug 25 – Sep 8

GarlicPlant cloves · Oct 6 – Nov 10

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 29) and first fall frost (Oct 20) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 21521 came on Mar 16 — 18 days earlier than the 1991–2020 average (Apr 3).

average
Apr 32026
Mar 16

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 6b in Maryland

590 plants native to the lower 48 states, recorded in Maryland, and rated by the USDA to survive −5 °F or colder — the bottom of zone 6b. Each links to its USDA PLANTS profile.

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in Barton, MD.

Soil in Barton, MD

The soil mapped at the center of ZIP 21521 is Gilpin — channery silt loam, well drained.

TextureChannery silt loama good balance for most vegetables

pH5.8moderately acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter3.41%moderate

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Gilpin channery silt loam, 20 to 35 percent slopes, moderately eroded.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 21521; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Barton, MD

Summer high81 °Faverage high, July

Winter low20 °Faverage low, January

Hot days6days a year at 90 °F or more

Freezing nights130nights a year at 32 °F or less

Growing degree days2,642base 50 °F — the season’s usable heat

Longest day14 h 58 mindaylight on June 21

Shortest day9 h 22 mindaylight on December 21

Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully

Precipitation41.4 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Savage Rvr Dam, MD (6 mi away); precipitation: Savage Rvr Dam, MD (6 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

5 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

215626b

Westernport, MD · 3 mi

215396a

Lonaconing, MD · 4 mi

Bloomington, MD · 5 mi

Maryland planting zones →

Questions about 21521

What planting zone is ZIP code 21521?

ZIP code 21521 (Barton, MD) is in USDA hardiness zone 6b on the 2023 map: the coldest night of an average winter reaches −5 to 0 °F (−20.6 to −17.8 °C).

When is the last frost in Barton, MD?

The median last spring frost (32 °F) near 21521 is April 29; after May 15 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Savage Rvr Dam station.

When is the first frost in Barton, MD?

The median first fall frost near 21521 is October 20, giving a median frost-free growing season of 174 days.

When should I plant tomatoes in 21521?

Start tomato seeds indoors around Mar 4 – Mar 18 and set transplants outside around May 6 – May 20, one to three weeks after the median last frost.

How much rain and snow does 21521 get?

About 41.4 inches of precipitation a year (NOAA 1991–2020 normals, Savage Rvr Dam station).

How hot do summers get in Barton, MD?

The average high peaks at 81 °F in July, with about 6 days a year at 90 °F or more.

What kind of soil does 21521 have?

The USDA soil survey maps Gilpin at the center of ZIP 21521: channery silt loam, well drained, pH about 5.8 (moderately acidic).

Did spring come early in Barton, MD in 2026?

Spring leaf-out near 21521 came on Mar 16 in 2026, 18 days earlier than the 1991–2020 average (Apr 3), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Barton, MD?

Intermediate onions: the longest day near 21521 is 14 h 58 min, so day-neutral types bulb best; long-day varieties may not bulb fully.